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While his deadline has slid back several times this year, people close to the Delaware Democrat say they expect him to join the Democratic primary fight next week.

Greg Schultz, a top political adviser who is preparing to oversee Biden's campaign, told Democrats on Capitol Hill earlier this week that "everything is going ahead as scheduled."

His entry into the race will answer one of the biggest remaining questions of the makeup of the crowded and historically diverse Democratic primary field. This would mark his third run for the White House.

Earlier this month, Biden said he planned to announce his decision "relatively soon."

"I've been told by the lawyer that I've got to be careful what I say so that I don't start the clock ticking and change my status," Biden told reporters. "... Even if I knew for certain that I was going to run for president back in Thanksgiving, my intention from the beginning, if I were to run, would be to be the last person to announce ... Give everybody else their day and then I get a shot and then we're off to the races."